School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom; The Nelson Mandela African Institute of Science and Technology, P.O. Box 447, Tengeru, Arusha, Tanzania.
Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
Sci Total Environ. 2015 Sep 15;527-528:520-9. doi: 10.1016/j.scitotenv.2015.04.037. Epub 2015 May 23.
This study examined the feasibility of nanofiltration (NF) and reverse osmosis (RO) in treating challenging natural tropical waters containing high fluoride and natural organic matter (NOM). A total of 166 water samples were collected from 120 sources within northern Tanzania over a period of 16 months. Chemical analysis showed that 81% of the samples have fluoride levels exceeding the WHO drinking guideline of 1.5mg/L. The highest fluoride levels were detected in waters characterized by high ionic strength, high inorganic carbon and on some occasions high total organic carbon (TOC) concentrations. Bench-scale experiments with 22 representative waters (selected based on fluoride concentration, salinity, origin and in some instances organic matter) and 6 NF/RO membranes revealed that ionic strength and recovery affected fluoride retention and permeate flux. This is predominantly due to osmotic pressure and hence the variation of diffusion/convection contributes to fluoride transport. Different membranes had distinct fluoride removal capacities, showing different raw water concentration treatability limits regarding the WHO guideline compliance. BW30, BW30-LE and NF90 membranes had a feed concentration limit of 30-40 mg/L at 50% recovery. NOM retention was independent of water matrices but is governed predominantly by size exclusion. NOM was observed to have a positive impact on fluoride removal. Several mechanisms could contribute but further studies are required before a conclusion could be drawn. In summary, NF/RO membranes were proved to remove both fluoride and NOM reliably even from the most challenging Tanzanian waters, increasing the available drinking water sources.
本研究考察了纳滤 (NF) 和反渗透 (RO) 在处理含有高氟和天然有机物 (NOM) 的挑战性热带天然水方面的可行性。在 16 个月的时间里，从坦桑尼亚北部的 120 个水源共采集了 166 个水样。化学分析表明，81%的水样氟含量超过世界卫生组织 (WHO) 1.5mg/L 的饮用水指南。氟含量最高的水样具有高离子强度、高无机碳和在某些情况下高总有机碳 (TOC) 浓度的特点。对 22 个具有代表性的水样（根据氟浓度、盐度、来源以及在某些情况下有机物进行选择）和 6 种 NF/RO 膜进行的中试实验表明，离子强度和回收率会影响氟的截留率和渗透通量。这主要是由于渗透压的影响，因此扩散/对流的变化会影响氟的传输。不同的膜具有不同的除氟能力，对于符合世界卫生组织指导方针的要求，不同的原水浓度有不同的处理能力限制。BW30、BW30-LE 和 NF90 膜在 50%回收率下的进料浓度限制为 30-40mg/L。NOM 的截留率与水基质无关，但主要受尺寸排阻控制。NOM 被观察到对氟的去除有积极影响。可能有几种机制起作用，但需要进一步研究才能得出结论。总之，NF/RO 膜被证明即使从最具挑战性的坦桑尼亚水中也能可靠地去除氟和 NOM，增加了可用的饮用水源。
